1. Field of the Invention
The present invention relates to an optical sensor device in which an optical sensor element is mounted on a package material using a glass substrate.
2. Description of the Related Art
In recent years, mobile terminals such as mobile personal computers, tablet personal computers, and smartphones are rapidly becoming widespread. This is because those mobile terminals have a large number of functions and another main reason is that they are designed to promote portability such as light in weight and thin in thickness. On the other hand, the number of electronic parts used in mobile terminals is numerous along with the pursuit of multi-functionality and portability, and further reduction in size, thickness, and cost and power saving are now always required. As a result, a resin mold package has been widely adopted for electronic parts. Behind the trend is common use of parts and materials. An optical sensor, which is one of mounting electronic parts responsible for reducing power consumption, is not exceptional. Similarly to other electronic parts, a resin mold package is often used to reduce the size, thickness, and cost.
FIG. 2 of Japanese Patent Application Laid-open No. 2007-36264 is a cross-sectional view of an illuminance sensor package in which a light receiving element is mounted on an insulating substrate made of a resin material and is molded by a resin. An electrode 4 is formed on the front surface of a resin substrate 1. The electrode 4 is wired so as to surround the rear surface of the substrate, thereby being connectable to the outside. The electrode 4 has an optical sensor element 2 mounted thereon. A top surface 2a of the optical sensor element 2 and the electrode 4 are electrically connected via a wire 6. The optical sensor element 2 is firmly fixed onto the electrode 4 by a conductive paste 5. The conductive paste 5 electrically connects the light receiving element 2 and the electrode 4 to each other. An electromotive force generated by light entering the top surface 2a of the optical sensor element 2 can be allowed to flow from the conductive paste 5 to the electrode 4 to be transferred to the outside.
In FIG. 2 of Japanese Patent Application Laid-open No. 2007-36264, the optical sensor element 2 is molded by a resin 11 as a whole. The resin 11 is made of a translucent resin, and an epoxy resin or the like is used. An infrared absorbing film 12 is provided on the resin 11. The infrared absorbing film 12 uses a resin and has a structure in which a liquid resin or a film is adhered and laminated on the resin 11. As the liquid resin, an epoxy resin or the like is used. In the case of using a film, a film is adhered on the resin 11 via a resin adhesive. With this, the optical sensor element 2 can receive visible light from which infrared light has been filtered, thereby serving as an optical sensor corresponding to the visibility. Such infrared absorbing effect can also be obtained even when an infrared absorbing substance used for the infrared absorbing film 12 is dispersed and mixed in the translucent resin 11.
However, the optical sensor device described in Japanese Patent Application Laid-open No. 2007-36264 has a package structure in which an epoxy resin or the like is used for sealing the element, and hence has a problem such as weak in environmental reliability including heat resistance and moisture resistance of the material. In particular, a resin or a film forming the infrared absorbing film is thin and weak against heat and moisture. Further, the infrared absorbing film needs to be adhered after the molding of an epoxy resin used for sealing the element and the curing of the epoxy resin. If a liquid resin or a film having the infrared absorbing function is repeatedly adhered on the cured resin, the adhesiveness of an adhesive layer is weakened. Accordingly, under an environment in which heat or moisture is added or an environment in which expansion and contraction are repeated with a temperature cycle repeating high temperature and low temperature as exemplified by a reliability test, the infrared absorbing film may consequently peel off easily.
Further, in the optical sensor device described in Japanese Patent Application Laid-open No. 2007-36264, as the infrared absorbing film for obtaining intended characteristics, a resin such as an epoxy resin is used as an example. In the case of using an epoxy resin or the like as the infrared absorbing film, the resin may be dissolved by moisture or heat. As a result, there is a problem that the infrared light as an absorption target cannot be absorbed and desired characteristics cannot be obtained progressively.
Further, in the optical sensor device described in Japanese Patent Application Laid-open No. 2007-36264, the element is molded by the transparent resin and the infrared absorbing film is provided only on the top surface of the optical sensor element. Accordingly, infrared light cannot be absorbed for light entering the optical sensor element from the side surface of the molding transparent resin or from an obliquely upward direction. As a result, there is a problem that light from which infrared light has not been absorbed also enters the optical sensor element, and desired characteristics cannot be obtained.
In light of the foregoing, some of electronic components which use glass as a package material have been commercially available. The glass material prevents moisture and contaminants from entering from outside and is also high in airtightness. The glass material has a coefficient of thermal expansion approximate to that of a silicon substrate forming a semiconductor element, and hence, when the semiconductor element is mounted on a glass package, the reliability of a mounting surface or a bonding surface can be enhanced. In addition, the glass material is inexpensive, and hence the increase in manufacturing cost can be suppressed.
FIG. 1 of Japanese Patent Application Laid-open No. Sho 61-214565 is a cross-sectional view of an illuminance sensor package in which an optical sensor element is mounted on a substrate made of a ceramic material and is hermetically sealed by an insulating frame and a transparent glass plate. On the front and rear surfaces of a ceramic substrate 11, wiring patterns 12 and 19 are provided by metallization, respectively, and are electrically connected to each other via a through electrode 18. An optical sensor element 13 is mounted on the substrate 11, and the top surface of the optical sensor element 13 and the wiring pattern 12 provided on the front surface of the substrate are electrically connected to each other via a wire 14. On the substrate, an insulating frame 15 is provided so as to surround the optical sensor element 13 and outside the portion at which the wire 14 is connected to the wiring pattern 12 from the top surface of the optical sensor element 13. The insulating frame 15 and the front surface of the substrate are adhered by a resin or the like. Transparent glass 17 is further adhered on the upper end of the insulating frame 15 by low-melting-point glass or the like.
The optical sensor element 13 is in a hollow state surrounded by the insulating frame 15 and the transparent glass 17. This is a structure in which the element and the wire are free from stress and protected, which is often a problem to be solved in a structure sealed by a resin mold. External light enters the top surface of the optical sensor element 13 through the transparent glass 17 to generate an electro motive force. The electro motive force generated by the optical sensor element 13 is transferred from the wire 14 through the wiring pattern 12 and the through electrode 18 to a wiring pattern 19 provided on the rear surface side of the substrate 11. The substrate 11 is not a multilayer but a single layer of the ceramic material, and, as the substrate material, a glass epoxy resin or the like is used as well as ceramic. Thus, the cost of the package is reduced.
The optical sensor device described in Japanese Patent Application Laid-open No. Sho 61-214565 does not use a resin which is used in the above-mentioned optical sensor device described in Japanese Patent Application Laid-open No. 2007-36264, but mainly uses a high-reliability material such as ceramic and glass. This can eliminate a weak portion, which is a problem inherent in the resin material. However, the optical sensor device described in Japanese Patent Application Laid-open No. Sho 61-214565 needs to be assembled with the use of different materials and parts such as the substrate, the insulating frame, and the transparent glass, and hence it is difficult to reduce the cost of the package. Further, the materials of the main components of the package, including the substrate, the insulating frame, and the transparent glass, have significantly different coefficients of expansion. Accordingly, under a temperature cycle test environment repeating high temperature and low temperature, the package is susceptible to damage due to stress generated by the difference in coefficient of expansion. In addition, the manufacturing of the package involves work of applying or printing low-melting-point glass or a resin and work of melting the low-melting-point glass or curing the resin. This results in problems that the reliability is partially low, the manufacturing process is long and complicated, and the manufacturing cost is difficult to reduce.
In the optical sensor device described in Japanese Patent Application Laid-open No. Sho 61-214565, the optical sensor element is surrounded by the insulating frame, and hence it is possible to remove light entering the element from the side surface and from an obliquely upward direction, which is a problem in the above-mentioned optical sensor device described in Japanese Patent Application Laid-open No. 2007-36264. However, the insulating frame is attached onto the substrate by adhesion in a later stage, and hence, as is understood from FIG. 1 of Japanese Patent Application Laid-open No. Sho 61-214565, the substrate needs to be designed to have larger dimensions than those of the insulating frame. Thus, there is a problem that the overall package size is difficult to reduce.